Approximately one third of new HIV infections occur as a consequence of drug abuse. Therefore, understanding the effects of drug abuse on AIDS remains an important goal CNS pathology in AIDS and many abused drugs, such as psychomotor stimulants, involve the neurotransmitter dopamine (DA). Predictibly, with DA insult there are also motor impairments in AIDS Because of the shared DA pathology, motor behaviors are likely to be doubly assaulted when AIDS and drug abuse are combined. The development of behavioral tests that are sensitive to CNS impairment is crucial to our understanding of the mechanisms behind the CNS pathology produced by AIDS. Demonstrating impairment earlier in the disease progression is necessary to identify which CNS changes are responsible for the CNS dysfunction associated with AIDS, and what mechanisms cause the dysfunction. Motor impairment has been shown to be a reliable marker for CNS impairment in AIDS, including impairment in cognitive function. This proposal will develop new procedures that will be incorporated into ongoing research on AIDS and abused drugs in macaques. A motor test that will simultaneously measure both behavioral and physiologic measures of fine motor control will be developed. This test, the "force and micro-tremor" test, will assess an animal's ability to regulate the amount of force with which it presses a rod Physiologic tremor will also be measured while the monkey presses the rod. Parameters of how much force should be required for each press, and how long the monkey should have to maintain the press will be investigated to determine the best method of measuring micro-tremor. The involvement of DA in the CNS pathology of both AIDS and many abused drugs makes understanding the effects of DA manipulations on this task important Increases and decreases in DA function will be assessed using pretreatments of cocaine and DAD 1 and D2 receptor antagonists, respectively. Once the parameters are established, the task will be trained in monkeys later infected with SIV, and the sensitivity of the task to SIV-induced motor impairment will be evaluated. The behavioral test developed in this proposal will be an important tool in our research on cognitive and motor consequences of AIDS and drug abuse, especially research on psychomotor stimulants and other drugs that have potential for damage to CNS dopaminergic systems.